The invention relates to a catalyst system for the gas-phase polymerization of conjugated dienes, consisting of a rare earth compound, an organoaluminium compound, a further Lewis acid, optionally a conjugated diene, an inert, inorganic or organic support material and, additionally, a co-catalyst applied to an inorganic or organic support material, with an improvement in the flowability of the rubber produced thereby.
Polybutadiene having a high content of cis-1,4 units has for a long time been produced on a commercial scale and used in the manufacture of tires and other rubber products.
For environmental reasons, attempts are being made to carry out the polymerization of this and other conjugated dienes in the gas phase, since no solvents have to be used in that case and emission and waste water pollution can be reduced.
In addition, novel rubbers having particular product properties can be produced by the process. In particular, fillers dispersed especially well in the polymer are obtained if they are present in the polymerization as the support for the active component of the catalyst.
It is already known from EP-B-0647657 that the polymerization of conjugated dienes, especially of butadiene, can be carried out in the gas phase, without the addition of solvents, if a catalyst system based on rare earth compounds and an organoaluminum compound on a particulate, inert, inorganic solid having a specific surface area greater than 10 m2/g (BET) and a pore volume of from 0.3 to 15 ml/g is used.
EP-B-0605001 claims the use of silica of a particular particle size as the support material and inert particulate materials to improve the flowability of tacky polymers.
EP-A-0442452 describes the use of inert particulate materials having particle diameters of from 0.01 to 10 xcexcm to improve the flowability of tacky polymers in the case of polymerizations above the softening temperature of the said tacky polymers.
EP-A-0530709 describes the use of inert particulate materials having particle diameters of from 0.01 to 150 xcexcm to improve the flowability of tacky polymers in the case of polymerizations above the softening temperature of the said tacky polymers.
In WO-88/02379 there is claimed the use of inert pulverulent inorganic materials in amounts of from 0.005 to 0.2 wt. %, based on the fluidized bed, to improve the flowability of polymers.
WO-96/04323 describes the use of inert particulate materials to improve the flowability of BR and IR in the case of polymerizations wherein the reactor temperature is below the dew point of one of the constituents of the circulating gas.
In EP-A-704464 there is described a resin particle having a tacky core and a non-tacky shell consisting of from 10 to 90% ethylene.
EP-A-570960 describes a resin particle having a tacky core and a non-tacky shell of inert particulate particles.
In all the processes described above, inert materials are used, with great importance being attached to the term inert.
U.S. Pat. No. 5,162,463, on the other hand, teaches that the agglomeration of the tacky particles in a fluidized bed can be avoided if an inert material coated with a polysiloxane coating is metered into the fluidized bed.
Finally, WO-97/08211 describes the addition of stabilizers in supported form.
It was completely unexpected to the person skilled in the art that, by using particulate materials coated with co-catalysts, it is possible very considerably to increase the activity of the catalyst system protected, inter alia, in EP-B-0647657 and consisting of
A) a rare earth alcoholate (I),
a rare earth carboxylate (II),
a complex compound of rare earths with diketones (III) and/or
an addition compound of the rare earth halides with an oxygen or nitrogen donor compound (IV), of the following formulae:
(RO)3Mxe2x80x83xe2x80x83(I)
(Rxe2x80x94CO2)3Mxe2x80x83xe2x80x83(II)

xe2x80x83and
MX3.y donorxe2x80x83xe2x80x83(IV),
B) an aluminum trialkyl, a dialkylaluminum hydride and/or an alumoxane of formulae (V) to (VII):
Al(H)x(R1)3-xxe2x80x83xe2x80x83(V)

xe2x80x83wherein in the formulae
M represents a trivalent rare earth element having an atomic number from 57 to 71,
the radicals
R, which may be the same or different, represent an alkyl radical having C1-C20,
the radicals
R1, which may be the same or different, represent a C1-C10-alkyl radical,
X represents chlorine, bromine or iodine,
x represents 0 or 1,
y represents from 1 to 6, and
n represents from 1 to 50,
C) a further Lewis acid, and
D) a particulate, inorganic or organic solid having a specific surface area greater than 10 m2/g (BET), a particle size of from 10 to 1000 xcexcm, preferably from 100 to 500 xcexcm, and a pore volume of from 0.3 to 15 ml/g (where carbon black is used, additionally having, a DBP adsorption of more a than 30 ml/100 g).
Suitable co-catalysts are all constituents having co-catalytic activity, especially the materials listed under B). Suitable support materials for these co-catalysts are all particulate materials, especially the materials listed under D).
If, on the other hand, a co-catalyst described under B) (e.g. aluminum alkyl) in liquid phase, whether it be in concentrated form or in dilute solution, is metered into the reaction chamber before and/or during the polymerization, the agitated reaction mass, for example in a stirred fixed bed or a fluidized bed, enters into an unstable state of fluidization as a result of spontaneous agglomeration and conglutination. The result is a drastically shortened useful life of the reactor. That is not the case if the supported co-catalyst solids according to the invention are metered into the gas-phase process and they are able to produce the desired action by intimate contact with the coated Nd catalyst described above or, inter alia, in EP-B-0647657. Furthermore, distribution within the reactor or the fluidized mass is markedly more homogeneous than is the case, for example, when a liquid co-catalyst material is injected into the reaction volume.
Also completely unexpected was the effect that the activity of the co-catalyst supported separately is markedly higher as compared with the same amount of co-catalyst supported together with the catalyst. The acceleration of the reaction, or increase in activity, achieved as a result of the co-catalyst""s being supported separately is far greater than 30%, as compared with the co-catalyst supported together with the catalyst.
In component A), M represents a trivalent rare earth element having an atomic number in the periodic system of from 57 to 71. Preference is given to those compounds in which M represents lathanum, cerium, praseodymium or neodymium or a mixture of rare earth elements that contains at least one of the elements lanthanum, cerium, praseodymium or neodymium in an amount of at least 10 wt. %. Particular preference is given to compounds in which M represents lanthanum or neodymium or a mixture of rare earths that contains lanthanum or neodymium in an amount of at least 30 wt. %.
There may be mentioned as radicals R in formulae (I) to (IV) in particular straight-chained or branched alkyl radicals having from 1 to 20 carbon atoms, preferably from 1 to 15 carbon atoms, such as methyl, ethyl, n-propyl, n-butyl, n-pentyl, isopropyl, isobutyl, tert-butyl, 2-ethylhexyl, neopentyl, neooctyl, neodecyl, neododecyl.
Examples of alcoholates of component A) are: neodymium(III) n-propanolate, neodymium(III) n-butanolate, neodymium(III) n-decanolate, neodymium(III) isopropanolate, neodymium(III) 2-ethylhexanolate, praseodymium(III) n-propanolate, praseodymium(III) n-butanolate, praseodymium(III) n-decanolate, praseodymium(III) isopropanolate, praseodymium(III) 2-ethylhexanolate, lanthanum(III) n-propanolate, lanthanum(III) n-butanolate, lanthanum(III) n-decanolate, lanthanum(III) isopropanolate, lanthanum(III) 2-ethylhexanolate, preferably neodymium(III) n-butanolate, neodymium(III) n-decanolate, neodymium(III) 2-ethylhexanolate.
Suitable carboxylates of component A) are: lanthanum(III) propionate, lanthanum(III) diethylacetate, lanthanum(III) 2-ethylhexanoate, lanthanum(III) stearate, lanthanum(III) benzoate, lanthanum(III) cyclohexanecarboxylate, lanthanum(III) oleate, lanthanum(III) versatate, lanthanum(III) naphthenate, praseodymium(III) propionate, praseodymium(III) diethylacetate, praseodymium(III) 2-ethylhexanoate, praseodymium(III) stearate, praseodymium(III) benzoate, praseodymium(III) cyclohexanecarboxylate, praseodymium(III) oleate, praseodymium(III) versatate, praseodymium(III) naphthenate, neodymium(III) propionate, neodymium(III) diethylacetate, neodymium(III) 2-ethylhexanoate, neodymium(III) stearate, neodymium(III) benzoate, neodymium(III) cyclohexanecarboxylate, neodymium(III) oleate, neodymium(III) versatate, neodymium(III) naphthenate, preferably neodymium(III) 2-ethylhexanoate, neodymium(III) versatate, neodymium(III) naphthenate. Particular preference is given to the use of neodymium versatate.
There may be mentioned as complex compounds of component A): lanthanum(III) acetylacetonate, praseodymium(III) acetylacetonate, neodymium(III) acetylacetonate, preferably neodymium(III) acetylacetonate.
Examples of addition compounds of component A) with donors which may be mentioned are: lanthanum(III) chloride with tributyl phosphate, lanthanum(III) chloride with tetrahydrofuran, lanthanum(III) chloride with isopropanol, lanthanum(III) chloride with pyridine, lanthanum(III) chloride with 2-ethylhexanol, lanthanum(III) chloride with ethanol, praseodymium(III) chloride with tributyl phosphate, praseodymium(III) chloride with tetrahydrofuran, praseodymium(III) chloride with isopropanol, praseodymium(III) chloride with pyridine, praseodymium(III) chloride with 2-ethylhexanol, praseodymium(III) chloride with ethanol, neodymium(III) chloride with tributyl phosphate, neodymium(III) chloride with tetrahydrofuran, neodymium(III) chloride with isopropanol, neodymium(III) chloride with pyridine, neodymium(III) chloride with 2-ethylhexanol, neodymium(III) chloride with ethanol, lanthanum(III) bromide with tributyl phosphate, lanthanum(III) bromide with tetrahydrofuran, lanthanum(III) bromide with isopropanol, lanthanum(III) bromide with pyridine, lanthanum(III) bromide with 2-ethylhexanol, lanthanum(III) bromide with ethanol, praseodymium(III) bromide with tributyl phosphate, praseodymium(II) bromide with tetrahydrofuran, praseodymium(III) bromide with isopropanol, praseodymium(III) bromide with pyridine, praseodymium(III) bromide with 2-ethylhexanol, praseodymium(III) bromide with ethanol, neodymium(III) bromide with tributyl phosphate, neodymium(III) bromide with tetrahydrofuran, neodymium(III) bromide with isopropanol, neodymium(III) bromide with pyridine, neodymium(III) bromide with 2-ethylhexanol, neodymium(III) bromide with ethanol, preferably lanthanum(III) chloride with tributyl phosphate, lanthanum(III) chloride with pyridine, lanthanum(III) chloride with 2-ethylhexanol, praseodymium(III) chloride with tributyl phosphate, praseodymium(III) chloride with 2-ethylhexanol, neodymium(III) chloride with tributyl phosphate, neodymium(III) chloride with tetrahydrofuran, neodymium(III) chloride with 2-ethylhexanol, neodymium(III) chloride with pyridine, neodymium(III) chloride with 2-ethylhexanol, neodymium(III) chloride with ethanol.
The rare earth compounds can be used individually or in admixture with one another.
A preferred embodiment is given to the use of neodymium versatate, neodymium octanoate and/or neodymium naphthenate as component A).
In formulae (V) to (VII) of component B), R1 represents a straight-chained or branched alkyl radical having from 1 to 10 carbon atoms, preferably from 1 to 4 carbon atoms. Examples of suitable aluminum alkyls of formula (V) are:
trimethylaluminum, triethylaluminum, tri-n-propylaluminum, triisopropylaluminum, tri-n-butylaluminum, triisobutylaluminum, tripentylaluminum, trihexylaluminum, tricyclohexylaluimium, trioctylaluminum, diethylaluminum hydride, di-n-butylaluminum hydride and diisobutylaluminum hydride. Preference is given to triethylaluminum, triisobutylaluminum and diisobutylaluminium hydride. Particular preference is given to diisobutylaluminium hydride.
The following are mentioned as examples of alumoxanes (VI) and (VII): methylalumoxane, ethylalumoxane and isobutylalumoxane, preferably methylalumoxane and isobutylalumoxane.
So-called Lewis acids are used as component C). Examples which may be mentioned are the organometal halides in which the metal atom belongs to group 3a) or 4a), as well as halides of the elements of groups 3a), 4a) and 5a) of the periodic system, as described in xe2x80x9cHandbook of Chemistry and Physicsxe2x80x9d, 45th edition, 1964-1965. Special mention is made of the following:
methylaluminum dibromide, methylaluminum dichloride, ethylaluminum dibromide, ethylaluminum dichloride, butylaluminum dibromide, butylaluminium dichloride, dimethylaluminum bromide, dimethylaluminum chloride, diethylaluminum bromide, diethylaluminum chloride, dibutylaluminum bromide, dibutylaluminum chloride, methylaluminum sesquibromide, methylaluminium sesquichloride, ethylaluminum sesquibromide, ethylaluminum sesquichloride, aluminum tribromide, antimony trichloride, antimony pentachloride, phosphorus trichloride, phosphorus pentachloride, tin tetrachloride.
There are preferably used diethylaluminum chloride, ethylaluminum sesquichloride, ethylaluminum dichloride, diethylaluminum bromide, ethylaluminum sesquibromide and/or ethylaluminum dibromide.
It is also possible to use as component C) the reaction products of aluminum compounds, as described as component B), with halogens or halogen compounds, for example triethylaluminum with bromine or triethylaluminum with butyl chloride. In that case, the reaction can be carried out separately, or the amount of the alkylaluminum compound required for the reaction is added to the amount required as component B).
Ethylaluminum sesquichloride, butyl chloride and butyl bromide are preferred.
There are used as component D) particulate, inorganic or organic solids having a specific surface area greater than 10 m2/g, preferably from 10 to 1000 m2/g (BET), a particle size of from 10 to 1000 xcexcm, preferably from 50 to 500 xcexcm, and a pore volume of from 0.3 to 15 ml/g, preferably from 0.5 to 5 ml/g. When carbon blacks are used, the DBP adsorption is used as a criterion for suitability in addition to the pore volume. The DBP adsorption is to be from 10 to 300 ml/100 g, preferably from 60 to 150 ml/100 g, particularly preferably from 90 to 130 ml/100 g.
The specific surface area (BET) is determined in the conventional manner according to S. Brunauer, P. H. Emmet and Teller, J. Anorg. Chem. Soc. 60 (2), 309 (1938), the pore volume is determined by the centrifugation method according to M. McDaniel, J. Colloid Interface Sci. 78, 31 (1980), and the DBP adsorption is determined according to DIN 53 601.
Suitable inorganic solids are in particular silica gels, precipitated silicas, clays, aluminosilicates, talcum, zeolites, carbon black, inorganic oxides, such as silicon dioxide, aluminum oxide, magnesium oxide, titanium dioxide, silicon carbide. Silica gels, precipitated silicas, zeolites and carbon black are preferred, with precipitated silicas and carbon black being especially preferred. Inert in this case is to be understood as meaning that the solids are of such a nature, or have been so pre-treated by means of pre-treatment, such as, for example, calcination, that the reactive surface does not hinder the formation of an active catalyst, or reacts with the monomers.
The mentioned inorganic solids, which satisfy the above-mentioned specification and therefore are suitable for use, are described in greater detail, for example, in Ullmanns Enzyclopxc3xa4die der technischen Chemie, Volume 21, p. 439 ff (silica gels), Volume 23, p. 311 ff (clays), Volume 14, p. 633 ff (carbon blacks), Volume 24, p. 575 ff and Volume 17, p. 9 ff (zeolites).
The inorganic solids can be used individually or in admixture with one another.
Suitable organic solids are also polymeric materials, preferably in the form of free-flowing powders, which are of such a nature, or have been so pre-treated by means of pre-treatment, such as, for example, drying, that the reactive surface does not hinder the formation of an active catalyst, or reacts with the monomers, have a particle size in the range of from 10 to 1000 xcexcm and which have a pore volume in the range of from 0.3 to 15 ml/g. An example of such a material is pulverulent polypropylene.
The molar ratio in which catalyst components A) to D) are used can be varied within wide limits.
The molar ratio of component A) to component B) is from 1:1 to 1:1000, preferably from 1:3 to 1:200, particularly preferably from 1:3 to 1:100. The molar ratio of component A) to component C) is from 1:0.4 to 1:15, preferably from 1:0.5 to 1:8.
From 0.1 mmol to 1 mol of component A), preferably from 1 to 50 mmol of component A), is used per 100 g of component D).
It is also possible to add to catalyst components A) to D) a further component E). Component E) is a conjugated diene, which may be the same as the diene which is subsequently to be polymerized with the catalyst. The use of butadiene and isoprene is preferred.
If component E) is added to the catalyst, the amount of E) is preferably from 1 to 1000 mol, based on 1 mol of component A), more preferably from 1 to 100 mol, based on 1 mol of component A). Particular preference is given to the use of from 1 to 50 mol of E), based on 1 mol of component A).
The supported co-catalyst according to the invention is prepared by applying a solution of the co-catalyst(s) preferably described under B) to the particulate solid D).
Preferably before, during and, optionally, after application of the co-catalyst solution, the solid is agitated, for example in a stirrer vessel with a conventional stirring unit, such as, for example, a cross-arm agitator or a helical ribbon impeller, or, in a further preferred form, in a plough-blade mixer.
Impregnation of the support material with co-catalyst solution can also take place in a fluidized bed. In that case, the active ingredient solution is applied, for example by spraying by means of a nozzle, to the support material which is fluidized by means of a stream of inert gas. Once the inert as has been freed of entrained solvent, it can be fed back into the reactor via an internal loop. The inert solvent can be re-used for preparing the active ingredient solution.
Since the co-catalyst system can react with air and/or moisture, it is advantageous to dry the solids powder D) before application of the co-catalyst solution, to remove the air and to maintain an inert gas atmosphere before, during and after application of the co-catalyst solution. Application of the co-catalyst solution is preferably so controlled that the added, preferably atomized, solution is immediately absorbed by the solid D). The formation of lumps and inhomogeneities is thus minimized.
The preparation of the catalyst system and/or supported co-catalyst according to the invention can also be carried out continuously.
Furthermore, by adjusting the ratio of the amount of supported co-catalyst material that is metered in to Nd catalyst that is present, it is possible to control the level of activity of the catalyst system. Preferably, the amount of co-catalyst solution applied to the solid should not be greater than the amount which the solid is able to absorb. Therefore, after application of the active ingredient solution, it is possible to continue stirring and agitating the solids powder gently as a free-flowing powder.
Although it is possible in principle to vary the amount of inert solvent used within wide limits, the amount is kept as small as possible, as discussed, for ecological and economical reasons. The amount is dependent on the amount and the solubility of the co-catalyst component(s) and on the pore volume/DBP adsorption of component D). An amount of from 10 to 2000 parts of the solvent, based on 100 parts of component D), is preferably used.
Preparation of the supported co-catalyst can take place in a wide temperature range. In general, the temperature is between the melting point and the boiling point of co-catalyst component B), or of the inert solvent. The operation is usually carried out at temperatures of from xe2x88x9220 to 100xc2x0 C., preferably from 20 to 40xc2x0 C.
In a preferred embodiment, the inert solvent is removed by distillation after the support material has been impregnated with active ingredient solution. The distillation can be carried out either in the same container in which the impregnation was carried out, or in a separate apparatus, for example a fluidized bed dryer. During removal of the solvent, the ingress of air and moisture must be avoided. Depending on the solvent used, the distillation is carried out at temperatures of from 0 to 150xc2x0 C., preferably from 10 to 80xc2x0 C., and at pressures of from 0.001 mbar to 20 bar absolute, preferably from 0.001 mbar to normal pressure. The distillation may also be carried out continuously. Without being worked up further, the condensate collected under inert conditions can be re-used as the solvent for the active ingredients used in the impregnation.
In a further preferred embodiment, the inert solvent is not removed.
The invention relates also to the use of the supported co-catalyst prepared according to the invention in a process for the polymerization of conjugated dienes, for example of 1,3-butadiene, isoprene, pentadiene or dimethylbutadiene, in the gas phase.
The polymerization is effected by bringing the gaseous conjugated diene into contact with the catalyst system described above or, inter alia, in EP-B-0647657 and with the supported co-catalyst prepared according to the invention. There may be added to the gaseous monomer further gases which serve either to dilute or to dissipate heat or to regulate the molecular weight. The polymerization can be carried out at pressures of from 1 mbar to 50 bar, preferably from 1 to 20 bar.
In general, the polymerization is carried out at temperatures of from xe2x88x9220 to 250xc2x0 C., preferably from 0 to 200xc2x0 C., particularly preferably from 20 to 160xc2x0 C.
The polymerization can be effected in any apparatus suitable for a gas-phase polymerization. Thus, for example, a stirred reactor, a rotary reactor or a moving-bed reactor, or a combination of those reactor types, may be used.
The resulting polymers have a cis-1,4 double bond content of approximately from 60 to 99%. The molar weight can be altered by means of the composition of the catalyst and by varying the polymerization conditions. Molar weights of from 103 to 106, measured by GPC (gel-permeation chromatography as described, for example, in M. Hoffmann, H. Krxc3x6mer, R. Kuhn, xe2x80x9cPolymeranalytik 1xe2x80x9d, Georg Thieme Verlag, Stuttgart, 1977, p. 349 ff with universal calibration) are usual.
The Mooney viscosity, ML (1+4xe2x80x2, 100xc2x0 C.)) is usually in the range of from 30 to 180 ME. By means of the polymerization in the gas phase it is also possible to prepare very high molecular weight polymers, which are obtainable by means of solution polymerization only with an extremely high outlay owing to the high viscosity and the possibility of transfer reactions by the solvent used.
The resulting polymers can be compounded and vulcanized in the conventional manner.
In a common embodiment, the procedure for the polymerization of 1,3-butadiene is as follows:
The catalyst system described above or, inter alia, in EP-B-0647657, after previously being mixed with the co-catalyst system prepared according to the invention, or separately therefrom, is transferred to an apparatus which is suitable for keeping the pulverulent catalyst and the supported particulate co-catalyst in motion. That may be effected, for example, by stirring, by rotation and/or by means of a stream of gas. The inert gas, for example nitrogen, which is initially present in the gas chamber is replaced by the gaseous monomer, whereupon polymerization starts immediately and the temperature rises. The monomer, optionally diluted, is fed with an inert gas to the reactor at such a speed that the desired reaction temperature is not exceeded. The reaction temperature can be adjusted in the conventional manner by heating or cooling. The polymerization is terminated by shutting off the supply of monomer. The polymer can be treated further in the known manner, by deactivating the catalyst and treating the polymer with known anti-ageing agents.
The Examples which follow are intended to explain the use of the catalyst system described herein for the gas-phase polymerization of conjugated dienes, consisting of a rare earth compound, an organoaluminum compound, a further Lewis acid, optionally a conjugated diene, an inert, inorganic or organic support material and, additionally, a co-catalyst applied to an inorganic or organic support material, with an improvement in the flowability of the rubber produced thereby, but without limiting it to the Examples, as well as the unexpected and marked increase in activity when the co-catalyst system according to the invention is used in addition to the above-described catalyst system.